As air travel has increased over the past decades, airport facilities have become more crowded and congested. Minimizing the time between the arrival of an aircraft and its departure to maintain an airline's flight schedule, and also to make a gate or parking location available without delay to an incoming aircraft, has become an airline priority. The safe and efficient ground movement of a large number of aircraft simultaneously into and out of the ramp and gate areas has become increasingly important. As airline fuel costs and safety concerns and regulations have increased, use of the aircraft main engines is no longer the best option for achieving the desired safe and efficient ground movement.
One of the various alternatives to the use of an aircraft's main engines to move an aircraft on the ground that has been proposed is the use of a motor structure integrally mounted with a wheel to rotate the wheel and drive the aircraft. The use of such a structure should move an aircraft during ground travel without using of an aircraft's main engines. U.S. Pat. No. 3,977,631 to Jenny describes a drive motor associated with aircraft gear wheels intended to drive an aircraft on the ground. In U.S. Pat. No. 7,445,178, McCoskey et al describe a powered nose aircraft wheel system with a multifunctional wheel motor coupled to the wheel axle and the wheel and located within the hub of the wheel. U.S. Pat. No. 7,226,018 to Sullivan additionally describes a wheel motor useful in an aircraft landing gear wheel designed to provide motive force to an aircraft wheel when electric power is applied. None of the foregoing patents, however, provides structure or method for dissipating heat or thermal distribution in the motors described therein.
U.S. Pat. No. 7,469,858 to Edelson, owned in common with the present invention, describes a geared wheel motor design that may be used to move an aircraft from a stationary position for taxiing. Published United States patent applications, including U.S. Patent Application Publication Nos. US2006/0273686 to Edelson, US2007/0282491 to Cox et al, and U.S. Pat. No. 7,975,960 to Cox, also owned in common with the present invention, describe aircraft drive systems that use electric drive motors to power aircraft wheels and move an aircraft on the ground. None of these patents or publications suggests a system for dissipating heat or enhancing thermal distribution in the disclosed electric motors. Commonly owned U.S. Patent Application Publication No. US2009/0152055 to Cox describes the cooling of brakes and other components in an aircraft undercarriage wheel with a drive means to propel the aircraft on the ground, wherein the drive means acts like a fan to provide air for cooling. There is no suggestion, however, of providing specific heat dissipation or thermal distribution structure for the drive means.
Cooling apparatus has been proposed for other kinds of vehicle electric drive motors. In U.S. Pat. No. 5,127,485, for example, Wakuta et al describe a cooling system for a compact, high torque wheel motor of the type used in golf carts and forklifts that has an oil reservoir in the lower part of the motor casing and requires an oil pump with a separate motor and a control circuit to direct oil flow that cools and lubricates the motor. Cooling fins are also provided to keep the motor at an acceptable temperature. It is not suggested that the oil reservoir of this system dissipates heat or that the system could function without the oil pump. U.S. Pat. No. 6,833,641 to Uchida et al and U.S. Patent Application Publication No. US2009/0195093 to Bandai et al both disclose the use of oil as a cooling fluid in electric drive motors. Uchida et al describes one oil reservoir in an upper area of the motor casing in communication with a second oil supply reservoir. It is not suggested that either reservoir dissipates heat or that this system would function effectively without both of these reservoirs. Bandai et al describes a single oil reservoir that provides oil to the motor in a storage chamber, wherein the bottom of the storage chamber functions as an oil pan so that rotation of the motor splashes it with oil. An electric motor radiator is also provided in this arrangement. Bandai et al does not suggest that the electric motor radiator could be eliminated. None of the foregoing art, moreover, suggests that the disclosed motor cooling arrangements could effectively dissipate heat and enhance thermal distribution during operation of an onboard non-engine powered electric drive assembly capable of powering one or more aircraft wheels to drive an aircraft on the ground.
A need exists, therefore, for a system to dissipate heat and enhance thermal distribution in an onboard non-engine powered drive assembly with a drive means that powers one or more aircraft wheels to drive the aircraft on the ground without directly using the aircraft engines. A need additionally exists for a drive means heat dissipation system that can be integrated with the aforementioned onboard non-engine powered drive means assembly drive means without changes to the existing aircraft landing gear components.